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However, not all glucosamine is created equal. “There’s a huge range in quality of these supplements,” says Dr. Boothe. To be sure you’re getting your money’s worth, stick with products that have been proven effective in studies. Both Dr. Gaynor and Dr. Boothe recommend products from NutraMax Labs, which manufactures Cosequin and Dasuquin. Glyco-Flex III, from Vetri- Science Labs, is also well researched, says Dr. Gaynor.

Methylsulfonylmethane (MSM).
Supplemental MSM appears to act as an analgesic (like aspirin). In a few small studies, it has improved pain and physical function in people with OA.

DL-phenylalanine (DLPA).
DLPA is a synthetic amino acid that seems to relieve pain. One component of DLPA, D-phenylalanine (DPA), has been shown to decrease chronic pain and boost the pain-relieving benefits of some medications (and of acupuncture) in animals and humans.

Avocado/Soybean Unsaponifiables (ASUs).
ASUs (the leftovers from soap production) act as anti-inflammatories, and can inhibit the breakdown of cartilage and promote its repair.

Perna canaliculus (Green-lipped Mussel).
Extracts from this New Zealand mollusk have been shown to reduce joint pain and swelling in arthritic dogs.
Pharmaceuticals
Nonsteroidal Anti-inflammatory Drugs, or NSAIDs. The go-to pain medications in nearly every vet’s arsenal are NSAIDs (NSAIDs for humans include aspirin and ibuprofen). The NSAIDs approved for use in dogs include Rimadyl,Metacam, Deramaxx, Previcox and Zubrin.

Of these, the first four are COX inhibitors (they target the cyclooxygenase, or COX, enzymes responsible for inflammation and pain). “Some dogs respond better to one, but they all have essentially the same mechanism,” says Dennis Caywood, DVM, MS, a diplomate with the American College of Veterinary Surgeons in Minneapolis.

The drug Zubrin blocks the COX enzymes as well as a second type of chemicals, called leukotrienes, meaning it addresses two different inflammation pathways. This could make it more powerful than the others, says Dr. Boothe. While NSAIDs can be very effective, they also carry the risk of side effects, including damage to the dog’s gastrointestinal tract. They require careful dosing, and can’t be combined with other NSAIDs.

Corticosteroids, or Glucocorticoids. Veterinary glucocorticoids, including prednisolone and methylated prednisolone (Cortisate-20, Depo-Medrol and Medrol), are steroidal medicines that attack inflammation. Unfortunately, they also attack the dog’s tissues.

“As a pharmacologist, I have a real bias against using steroids to treat chronic pain,” says Dr. Boothe. Glucocorticoids can cause weight gain, incontinence and lethargy. Long-term, they’ve been linked to compromised immunity,muscle and bone loss, and a potentially fatal shutdown of the adrenal glands. Moreover, glucocorticoids actually damage cartilage. “Veterinarians have used them in older animals with the idea that they were the only thing that would relieve the dog’s pain,” says Dr. Boothe. “But now there are better options.” However, she says, glucocorticoids might be used in a one-time, direct-tothe- joint injection (see hyaluronic acid, following).

Narcotics.
Tramadol (Ultram) is a synthetic opiate. It’s strictly a pain reliever, says Dr.Gaynor, not an anti-inflammatory, so it can be safely combined with NSAIDs and many other drugs.
Medicines for Neuropathic Pain.
Two drugs for humans, gabapentin and amantadine, also address the neurologic components of dogs’ pain—how the pain messages are carried to the dog’s spinal cord and brain. These drugs also reduce “windup,” a phenomenon in which a dog’s nerves become overly sensitized, leading her to feel pain from things that otherwise wouldn’t hurt at all.

Injectable PSGAGs.
Adequan is a prescription PSGAG that works like glucosamine and chondroitin, only faster, says Dr. Boothe.